I've already seen some different answers, but none of these helped me...
This is the trick: I have to fix this without touching the Gemfile. I'm currently creating my working environment so that it matches the production server, so, I cannot modify the rails' code at all.
My OS: OSX 10.11
Ruby: ruby 2.0.0p643
Rails: 4.0.0
The gem is the Gemfile as gem 'mysql2'. There are no errors when doing bundle install, but when I try to rake db:migrate --trace this is the output:
rake aborted! There was an error while trying to load the gem 'mysql2'. /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/bundler-1.11.2/lib/bundler/runtime.rb:80:in `rescue in block (2 levels) in require' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/bundler-1.11.2/lib/bundler/runtime.rb:76:in `block (2 levels) in require' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/bundler-1.11.2/lib/bundler/runtime.rb:72:in `each' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/bundler-1.11.2/lib/bundler/runtime.rb:72:in `block in require' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/bundler-1.11.2/lib/bundler/runtime.rb:61:in `each' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/bundler-1.11.2/lib/bundler/runtime.rb:61:in `require' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/bundler-1.11.2/lib/bundler.rb:99:in `require' /Users/redar/redar/config/application.rb:7:in `<top (required)>' /Users/redar/redar/Rakefile:4:in `require' /Users/redar/redar/Rakefile:4:in `<top (required)>' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/rake-10.1.0/lib/rake/rake_module.rb:25:in `load' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/rake-10.1.0/lib/rake/rake_module.rb:25:in `load_rakefile' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/rake-10.1.0/lib/rake/application.rb:637:in `raw_load_rakefile' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/rake-10.1.0/lib/rake/application.rb:94:in `block in load_rakefile' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/rake-10.1.0/lib/rake/application.rb:165:in `standard_exception_handling' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/rake-10.1.0/lib/rake/application.rb:93:in `load_rakefile' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/rake-10.1.0/lib/rake/application.rb:77:in `block in run' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/rake-10.1.0/lib/rake/application.rb:165:in `standard_exception_handling' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/rake-10.1.0/lib/rake/application.rb:75:in `run' /Users/redar/.rvm/gems/ruby-2.0.0-p643/gems/rake-10.1.0/bin/rake:33:in `<top (required)>' /Users/redar/.rvm/gems/ruby-2.0.0-p643/bin/rake:23:in `load' /Users/redar/.rvm/gems/ruby-2.0.0-p643/bin/rake:23:in `<main>' /Users/redar/.rvm/gems/ruby-2.0.0-p643/bin/ruby_executable_hooks:15:in `eval' /Users/redar/.rvm/gems/ruby-2.0.0-p643/bin/ruby_executable_hooks:15:in `<main>'
I don't know how to interpret this. Is there something wrong with the Rakefile?
Also, this is the output from the mkmf.log
EDIT: This is the content of my Rakefile, located at myapp/folder
# Add your own tasks in files placed in lib/tasks ending in .rake,
# for example lib/tasks/capistrano.rake, and they will automatically be available to Rake.
require File.expand_path('../config/application', __FILE__)
MyApp::Application.load_tasks
